The present invention generally relates to a machining apparatus and more particularly, to a lead face machining apparatus for accurately machining a lead face and a cylindrical surface of a cylindrical work.
For components each having a lead face formed on a cylindrical surface thereof as generally shown in FIG. 1, there is recently a sharply increasing demand for recording/reproducing cylinders for use in cassette video recorders for domestic use (helical type video tape recorders) in the field of electric industry. The cylinder comprises a fixed cylinder 1 having a cam curve shown in a development view of FIG. 2, and a rotational cylinder 2 (accommodating a magnetic head therein) rotatably provided coaxially with the fixed cylinder 1. A magnetic tape 3 is provided so as to extend over the fixed cylinder 1 and rotational cylinder 2, and is arranged to run slowly along a lead face 4 of the fixed cylinder 1. The rotational cylinder 2 is rotated at a speed of a few m/sec. such that scanning is performed at the relative speed by the magnetic head, whereby video signals are recorded in magnetic tracks A.sub.1 each having a width of approximate 20 .mu.m. On the other hand, when pictures are to be reproduced on a screen of a television receiver, the magnetic head is required to rescan the same magnetic tracks as those scanned during recording with an error of within 2 to 3 .mu.m or less. Meanwhile, since the magnetic tape is made of a soft polymer tape having a magnetic material coated on opposite surfaces thereof, the lead face 4 and cylindrical surface 5 of the fixed cylinder 1, both acting as guideways for the magnetic tape 3 are required to be smooth and to be made of non-magnetic material and therefore, are generally made of aluminum alloy. Accordingly, in order to obtain an accuracy of 2 to 3 .mu.m and a smooth machined surface, the fixed cylinder 1 has been manufactured by cutting operations.
Conventionally, in order to machine workpieces having such a lead face and a cylindrical surface as described above, it has been a general practice that general purpose machines such as a lathe, a milling machine, etc. are employed or special purpose machines such as a cam forming machine, etc. are utilized. However, these known methods have been disadvantageous in that it is difficult to machine the workpieces at the above-described accuracy efficiently.
Furthermore, although, as disclosed in Japanese Utility Model Publication No. 23789/1980 (Jikkosho No. 55-23789), there has been proposed a method in which a cylindrical surface and a lead face are machined by a special purpose machine in accordance with a lead cam separately provided, this prior art method has such disadvantages that the special purpose machine becomes complicated in structure and therefore, is liable to vibrate.